1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and to a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member. More particularly, it relates to an electrophotographic photosensitive member having a cylindrical support, a photosensitive layer provided on the outer-periphery side of the cylindrical support, and an insert member inserted into the cylindrical support on its inner-periphery side, and to a process cartridge and an electrophotographic apparatus which have such an electrophotographic photosensitive member.
2. Related Background Art
In electrophotographic systems, commonly used is a system employing a process in which an electrostatic latent image is formed by charging and exposure (imagewise exposure), on the surface of an electrophotographic photosensitive member having a cylindrical support and a photosensitive layer provided on the outer-periphery side of the cylindrical support, this electrostatic latent image is developed with a toner to form a toner image, and this toner image is transferred to a transfer material, such as paper, to obtain an image-formed material (a copy or a print). Also, the surface of the electrophotographic photosensitive member, from which the toner image has been transferred, is cleaned as the occasion requires.
In electrophotographic apparatus employing this process, noises may come from various sources.
The charging of the surface of the electrophotographic photosensitive member may be one source from which a noise may be produced.
As charging assemblies, corona charging assemblies, which are non-contact charging assemblies, have conventionally been in versatile use. In recent years, however, contact charging assemblies have been put into practical use, in which the surface of an electrophotographic photosensitive member is charged by applying a voltage from an external power source to a contact charging member disposed in contact with the electrophotographic photosensitive member.
As the contact charging assemblies, from the viewpoint of charge uniformity, commonly used are assemblies in which the surface of an electrophotographic photosensitive member is charged by applying an oscillating voltage from an external power source to the contact charging member, the oscillating voltage being formed by superimposing on a DC voltage of about 1 to 2 kV an alternating voltage having a peak-to-peak voltage Vp-p of about 2 kV.
However, the contact charging member to which such an oscillating voltage is kept applied repeats its contact with, and separation from, the electrophotographic photosensitive member, and hence the electrophotographic photosensitive member may vibrate to cause a noise called charging noise.
The cleaning of the surface of the electrophotographic photosensitive member may also be another source of noise.
As electrophotographic photosensitive members are being made highly durable in recent years, a larger force of friction may act between an electrophotographic photosensitive member and a cleaning member, so that a vibration sound (noise) may occur between the electrophotographic photosensitive member and the cleaning member. This is a vibration sound which comes where the stick-slip vibration increases especially at the time the electrophotographic photosensitive member is rotated at a low speed, e.g., at the time it begins to be rotated or at the time it stops to be rotated, and the electrophotographic photosensitive member vibrates in excess.
As one of methods for preventing such noises, it is known to force an elastic material or an insert member made of resin or metal, into a cylindrical support on its inner-periphery side, of an electrophotographic photosensitive member (Japanese Patent Application Laid-open No. H05-035048, etc.).
Various methods are also known that relate to the shape of the insert member and how to fasten it (Japanese Patent Applications Laid-open No. 2000-089612, No. 2000-098804, etc.).
However, where the insert member is fastened with an adhesive to the cylindrical support on its inner-periphery side, no sufficient adhesive force is achievable unless the insert member has a proper shape, and it may come about that the insert member unfastens from the cylindrical support when the electrophotographic photosensitive member or process cartridge is in distribution in the market or when it is in use in an electrophotographic apparatus.
For example, the above Japanese Patent Application Laid-open No. 2000-089612 discloses a technique in which the insert member is tapered at its edges so that the insert member may not be caught when it is inserted into the cylindrical support on its inner-periphery side, to improve productivity.
However, the insert member having such a shape affords only small adhesion clearances between the inner-periphery side of the cylindrical support and the insert member, and hence no sufficient adhesive force has been achievable.
Especially when one composed chiefly of a resin is used as the insert member, the resin has so large a heat shrinkage in many cases that a stronger adhesive force is required.
A method is also available in which the insert member is fastened to the cylindrical support on its inner-periphery side by press fitting, without the use of any adhesive. However, if the insert member is press-fitted and fastened to such an extent that it does not start (or slip), the electrophotographic photosensitive member may have so poor a dimensional precision as to cause image density non-uniformity.